Smoking articles, such as cigars, cigarettes, and pipe tobaccos are conventionally made from blends of shredded tobacco lamina, shredded reconstituted tobacco, tobacco shreds, fillers, and mixtures thereof. In addition, the tobacco used will come from varying sources commonly identified as air-cured tobacco, flue-cured tobacco, or mixtures thereof. It has long been desired to use, in addition to the lamina portion of the tobacco leaf, the stem portions which include the mid-ribs, veins, and also the tobacco stalk.
Present tobacco manufacturing procedure includes processing the tobacco leaf through a stemmery which separates the stems, including mid-ribs, from the lamina. The proportion of stems will vary somewhat but generally the stem materials will represent 20 to 25% by weight of the total tobacco leaf. These materials are not presently successfully utilized as such in smoking articles because of their hard, horny nature. In addition, they are generally unsuitable for smoking articles such as cigarettes because of their poor burning properties and because their sharp, hard edges tend to tear the wrapping paper.
Efforts attempted in the past to render the stem materials suitable for use have included passing the stems between rollers which act to crush or disintegrate the stems and/or cutting the stems. This has not been fully satisfactory because the resultant material is still hard and has a very limited filling capacity. In addition, many cross-sectional pieces, or bird's eyes, result together with other woody, sharp pieces which can penetrate the paper wrapper of a cigarette, deform the shape thereof, and which tend not to burn properly.
As to filling capacity, this has been improved by treatment of the stems with water and/or solvents in efforts to expand the same and thereby increase the filling capacity. Where excessive water has been used, this has proven unsuitable since it results in the leaching, and consequently the loss, of the water-soluble materials in the stems, thus adversely affecting the desirable tobacco properties such as smoke flavor and taste. Solvent treatment is also unsuitable in that it may add an element to the tobacco not normally found therein.